Question

Which among the following does not cause hyperpyrexia?

• A. MAO inhibitors
• B. Alcohol
• C. TCAs (tricyclic antidepressants)
• D. Amphetamine

Hint:

Which agent dilates skin vessels and tends to cause hypothermia instead?

Answer 1

The Correct Option is B

This is an odd-one-out question about thermoregulation. Three of the listed agents push temperature up; one pulls it down, and that is the answer.

Monoamine oxidase inhibitors flood synapses with serotonin and noradrenaline, and when combined with other serotonergic drugs or tyramine-rich food they can ignite serotonin syndrome or a hyperadrenergic crisis, both of which feature dangerously high temperatures. Tricyclic antidepressants block muscarinic receptors, and the resulting anticholinergic state (hot, dry, flushed skin with impaired sweating) raises core temperature in overdose. Amphetamine is a stimulant that ramps up cellular metabolism, muscle activity and agitation while constricting skin vessels, a recipe for stimulant hyperthermia.

Ethanol behaves in the opposite direction. It dilates skin blood vessels, so heat is lost rapidly to the environment, and it depresses the central nervous system including hypothalamic temperature control. The practical result, especially in cold surroundings, is a drop in body temperature and a risk of hypothermia rather than fever. Hence alcohol is the agent that does not cause hyperpyrexia.
\[\boxed{\text{Alcohol}}\]